The present invention is directed to a current-fed push-pull converter and, in particular, to a current-fed push-pull converter having a step-down regulating means and a transformer means that is push-pull controlled.
For generating a plurality of stable output DC voltages from a prescribed input DC voltage that, for example, is generated in a power pack that is isolated from electrical mains and is interruption-free, a plurality of individual step-down voltage regulators connected in parallel can be provided, each of which generates a respective output DC voltage. Since every step-down voltage regulator forms a separate unit and a corresponding plurality of such units are employed, the number of general components, as well as, magnetic components is extremely high. One possibility for reducing the general components outlay is the use of a two-transistor single-ended forward converter having a plurality of output windings to each of which is connected a respective storage inductor. However, this does not eliminate the significant outlay for magnetic components.
Furthermore, adverse influencing of the output DC voltages relative to one another occurs for fluctuations in loads connected to individual outputs. The prerequisites for preserving the relative voltage levels of the output DC voltages are established by using a current-fed push-pull forward converter having a plurality of output windings. The outlay for magnetic components, however, is still relatively great. Although the number of storage inductors used on the secondary side within the arrangement is reduced to a single storage inductor on the primary side, the outlay for magnetic components is still relatively high because a full transformer, that is a transformer having at least separate primary and secondary windings, continues to be employed as a transformer unit which implies relatively large dimensions particularly when high powers are to be supplied.
Step-down voltage regulators are well known in the prior art. In particular, specific designs of step-down voltage regulators are known, for example the designs of two-transistor single-ended forward converters or of current-fed push-pull converters. Corresponding basic circuits are disclosed, for example, in Elektronik 1978, No. 4, pages 102-107, particularly FIGS. 4, 9 and 13.